1. Field of the Invention
This invention relates to an engine malfunction detection system, particularly a malfunction detection system of an internal combustion engine, more particularly to a malfunction detection system of equipments such as an alternator (alternating current electrical generator), a sensor or switch, that are connected to an internal combustion engine.
2. Description of the Related Art
Usually, an internal combustion engine is provided with equipments including an alternator, sensors (switches) that generate outputs and has an electronic control unit (ECU) constituted as a microcomputer. The ECU is supplied with the power generated by the alternator to operate and computes manipulated variables to control the operation of the engine based on the outputs sent from the sensors and switches.
In such an engine, if one or all of the equipments has malfunctioned, it becomes difficult to control the engine as desired. For that reason, as regards a crank angle sensor output indicative of a signal indicative of a reference piston position, Japanese Laid-Open Patent Application No. Hei 9 (1997)-105350 teaches removing as noise an output generated by the sensor that is less than an effective crank angular value.
While this prior art system does disclose eliminating the influence of noise in the sensor outputs and does not disclose detecting the malfunction of equipments, it is desirable to detect or discriminate the malfunction of equipment connected to the engine
An object of the present invention is therefore to provide an engine malfunction detection system which detects or discriminates malfunction of equipment that is connected to the engine.
For realizing this object, there is provided a system for detecting malfunction of an equipment that is connected to an internal combustion engine and generates an output; comprising; output discriminating means for discriminating periodically for a predetermined period of time whether the output of the equipment is within a predetermined range; counting means for counting a number of times that the output of the equipment is discriminated to be out of the predetermined range; and malfunction determining means for comparing the count with a reference value and for determining that the equipment has malfunctioned when the count is equal to or greater than the reference value.